MVC Questions & Answers

In this article , will discuss about basics of MVC , so if you are planning for MVC interview so just go through it , it will help a lot to crack it or add more technical knowledge about MVC.

1)    Explain what is MVC?

MVC is an Acronym of Model View Controller and it is an Architectural pattern to develop Web Applications.

2)    What are the main components of MVC?

There are three main components of MVC that is Model , View and Controller so lets take a idea about these

Model – Model represents business logic where we put our logic like transformation logic and presentation logic.

View- View is simple User interface and shows our application look and feel.

Controller – It is main component of MVC that takes request from the end user and  bind view model view with model and finally send response back to browser.

MVC also defines application into 3 logical layers

·         Presentation Layers – showing via View

·         Business Layer – showing via Model

·         Input Layer   -showing via Controller

3)    What are Actions?

Action is the methods or function that is last end point for every request and Every controller have default action method as Index that is defined in RouteConfig.cs in route.

4)    Explain Advantages of MVC.

MVC have various advantages but below are two main advantages

·         Separation Of Concern – It provide an separation of concern means In MVC Code behind is converted to separate class file and this is achieved through Model , View and controller so Our UI components does not depend directly to our code behind.

·         Ease of Unit Testing – As Code behind , has been transferred to a separate class file so that It is easy to create a unit test as all controller is just a class so we can pass the appropriate input for Unit testing and get the Response.

·         Now we can maintain out application easily because of separation of concern

·         In the same time , we can split work to many developers , it will not affects one developer work to other.

5)    What is Routing?

Routing is a URL mapping mechanism in MVC that decides which action method of a controller class to executed.  Every incoming request goes through this process and it is by default in MVC.

To map routing , First we have to register it in Global.asax.cs via Application_Start method and then define routes in RouteConfig.cs  as below

public static void RegisterRoutes(RouteCollection routes)

        {

            routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

            routes.MapRoute(

                            name: "Default",

                            url: "{controller}/{action}/{id}",

                            defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }

                        );

        }

6)    How many return type of Action method available in MVC?

Action can have many return types as below

·         ViewResult – return HTML and markup

·         JsonResult  - return json

·         EmptyResult -return no response

·         ContentResult – return string literal

·         JavaScriptResult -return javascript script

·         RedirectResult – redirect to new url or action or controller

·         RedirectToRouteResult – return to new route defined as per route table

·         PartialViewResult – return html

·         FileContentResult/FileStreamResult/FilePAthResult – return content of  file

·         HttpUnauthorizedResult -return HTTP 403 status

7)    What is scaffolding?

Scaffolding is a code generation framework for web application and it generates code for CRUD operation, It is quite good for new developers and also provides basic functionality like Login , Register with bootstrap , so developer can easily learn.

8)    Difference between each version of MVC 2, 3 , 4, 5 and 6?

MVC 6

·         ASP.NET MVC and Web API has been merged in to one.

·         New JSON based project structure.

·         Side by side - deploy the runtime and framework with your application

·         Dependency injection is inbuilt and part of MVC.

·         Everything packaged with NuGet, Including the .NET runtime itself.

·         No need to recompile for every change. Just hit save and refresh the browser.

·         Compilation done with the new Roslyn real-time compiler.

MVC 5

·         Authentication Filters

·         Attribute based routing

·         Asp.Net Identity

·         Bootstrap in the MVC template

·         Filter overrides

MVC 4

·         ASP.NET Web API

·         New mobile project template

·         Many new features to support mobile apps

·         Refreshed and modernized default project templates

MVC 3

·         Razor

·         JavaScript and Ajax

·         Support for Multiple View Engines

·         HTML 5 enabled templates

·         Model Validation Improvements

MVC 2

·         Templated Helpers

·         Client-Side Validation

·         Areas

·         Asynchronous Controllers

·         Html.ValidationSummary Helper Method

·         DefaultValueAttribute in Action-Method Parameters

·         Binding Binary Data with Model Binders

·         DataAnnotations Attributes

·         Model-Validator Providers

·         New RequireHttpsAttribute Action Filter

9)    Difference between MVC and three 3 Layered Architecture

·         3 tier divides the whole app in: UI, logic and data

·         MVC divides the UI part in: view (kind of UI of the UI), model (data) and controller (logic)

10) How to maintain State in MVC

State can be managed in MVC by

1.     Hidden Field

2.     Session

3.     ViewData

4.     ViewBag

5.     Session

11) Difference between ViewData and ViewBag?

            1. both are used to send data from Controller to View

            2. Usage

In Controller

                        ViewData[“Data”] =”Test”;

                        ViewBag.Data = “Test”;

In View

                        ViewData[“Data”]          

                        ViewBag[“Data”]

            3. ViewBag is dyanamic wrapped and internally use dynamic keyword introduced in C#4.0

            4. ViewData needs typecasting in case of complex type while ViewBag doesn’t need.

12) What is TempData?

·         TempData is used to send data from Controller to controller or Controller to Action

·         TempData is used to pass data from the current request to the next request

·         It keeps the information for the time of an HTTP Request. This means only from one page to another. It helps to maintain the data when we move from one controller to another controller or from one action to another action

·         It requires typecasting for complex data type and checks for null values to avoid error. Generally, it is used to store only one time messages like the error messages and validation messages

13) How to maintain TempData request for subsquent Request and what is keep and peek?

TempData data is not available for subsequent request if data is read so As per read we are having two methods one is keep  and usage are

first read then keep

string data= @Html.TempData[“Data”];

@Html.TempData.keep(“Data”);

Peek also do the same work but it just read the tempdata and also advice to TempData to provide it for next request as below

String str = @TempData.peek(“Data”).ToString()

14) What are partial Views?

Partial view is a reusable view  like a user control in web forms which can be embedded inside other view. For example let’s say all your pages of your site have a standard structure with left menu, header, and footer

For every page you would like to reuse the left menu, header, and footer controls. So you can go and create partial views for each of these items and then you call that partial view in the main view.

15) What is the difference between View and Partial View?

View

·         View is not lightweight as compare to Partial View.

·         It contains the layout page.

·         View might have markup tags like body, html, head, title, meta etc.

·         Before any view is rendered, viewstart page is rendered.

Partial View:

·          It does not contain the layout page.

·         We can pass a regular view to the RenderPartial method.

·         Partial view does not verify for a viewstart.cshtml.We cannot put common code for a partial view within the viewStart.cshtml.page.

·         Partial view is designed specially to render within the view and just because of that it does not consist any mark up.

16) What are Filters in MVC?

In MVC, controllers define action methods and these action methods generally have a one-to-one relationship with UI controls such as clicking a button or a link, etc. For example, in one of our previous examples, the UserController class contained methods UserAdd, UserDelete, etc.

But many times we would like to perform some action before or after a particular operation. For achieving this functionality, ASP.NET MVC provides feature to add pre and post action behaviors on controller's action methods.

Types of Filter

ASP.NET MVC framework supports the following action filters,

Action Filters

Action filters are used to implement logic that gets executed before and after a controller action executes. We will look at Action Filters in detail in this chapter.

 Authorization Filters

Authorization filters are used to implement authentication and authorization for controller actions

Result Filters

Result filters contain logic that is executed before and after a view result is executed. For example, you might want to modify a view result right before the view is rendered to the browser.

Exception Filters

Exception filters are the last type of filter to run. You can use an exception filter to handle errors raised by either your controller actions or controller action results. You can also use exception filters to log errors.

Action filters are one of most commonly used filters to perform additional data processing, or manipulating the return values or cancelling the execution of action or modifying the view structure at run time.